1. Field of the Invention
The present invention relates to radar detectors and more specifically to a radar detector for detecting a target immersed in clutter.
2. Description of the Prior Art
A polarized radar signal incident upon clutter will become depolarized upon reflection so that the signal returned to the receiver will have a polarization different from that of the transmitted signal. The nature of this polarization transformation will vary with the polarization of the signal incident on the target. An approach to this problem is described in U.S. Pat. No. 4,323,898 granted to Richard M. Barnes et al and assigned to the present assignee. The returned signal is received by antennas responsive to orthogonally polarized components of the reflected signal. The received orthogonal signal components are modified and analyzed in a processor which detects the polarization of the reflected signals by estimating the Stokes parameters of the received signal which may then be used to generate detection criteria that are compared to a predetermined threshold level.
U.S. Pat. No. 4,323,899 issued to Richard M. Barnes et al and assigned to the present assignee concerns apparatus similar to that described in U.S. Pat. No. 4,323,898 but employing means to analyze the reflected signals as received by estimating the Stokes parameters of the signals and using these parameters to generate detection criteria that are compared to a predetermined threshold level. The presence of a target is indicated when the detection level criterion exceeds the threshold level.
The present invention provides means to obtain a complete polarization signature of the target, representing all possible illumination polarizations, in a single transmission. Although the aforementioned prior art devices might be modified to generate a complete polarization signature, this would require a number of sequential transmissions, which would be unsuitable if the target should move during the sequence of transmissions.